1. Field of the Invention
The present invention relates to a semiconductor packaging mold and a method of manufacturing a semiconductor package using the same.
2. Description of the Related Art
A semiconductor wafer is cut into a plurality of single semiconductor chips through a sawing process in an overall assembly process. Each of the semiconductor chips is mounted on a lead frame or a basic frame such as a printed circuit board through a die attaching process. The semiconductor chip, e.g., as mounted on the frame, goes through a wire bonding process whereby a bond pad of the chip electrically connects to a connection terminal of the frame, e.g., by way of a gold wire.
To prevent damage from external impact, the assembly of the semiconductor chip and the frame, as interconnected by the gold wire, is encapsulated by a sealant, e.g., a resin such as an epoxy mold compound, through a molding process.
In recent years, the semiconductor package has been reduced in thickness and increased in the number of pins and in the clock speed. Due to this, undesirably, the semiconductor package generates a large amount of heat. Therefore, many schemes have been developed for effectively discharging heat, as generated within the semiconductor package, to an external side of the package.
One of the schemes integrates a heat spreader within the semiconductor package during the molding process. The heat generated from the semiconductor package is transmitted to atmosphere or to the frame through the heat spreader and is thereby discharged at the external side, thereby protecting electrical properties of the semiconductor package against heat-related deterioration.
To maximize the heat discharge efficiency, the heat spreader as integrated with the semiconductor package is partly exposed at the external side. To accomplish this exposure, therefore, the molding process is performed in a state where a surface of the heat spreader closely contacts a mold cavity surface. In other words, the process aims to prevent resin from flowing or “bleeding” between the mold cavity surface and the heat spreader. Thus, the resin must not cover the external surface of the heat spreader. Undesirably, the sealing resin sometimes bleeds and thinly covers the surface of the heat spreader, and a resin bleed defect results.
FIG. 1 shows a semiconductor package illustrating the resin bleed defect and FIG. 2 shows an enlarged view of a portion A of FIG. 1.
Referring to FIGS. 1 and 2, a typical semiconductor package 30 includes a basic frame 10 such as a printed circuit board, a semiconductor chip 14 physically mounted on the basic frame 10 by a die adhesive 12 and electrically connected to the basic frame 10 by a gold wire 16. A sealing resin 20 encapsulates the semiconductor chip 14 on the basic frame 10. To effectively discharge the heat generated from the semiconductor chip 14 to an external side, a heat spreader 18 is integrated with the semiconductor chip 14 during a molding process and remains partly exposed as an external side of the semiconductor package 30. A plurality of solder balls 22 attach on a bottom of the basic frame 10 to serve as external connection terminals.
In the molding process, to prevent the resin bleed defect, a surface of the heat spreader, which is to remain exposed, must accurately and closely contact an upper mold body 24 (FIG. 2) of the mold. Undesirably, when a ram pressure for filling the sealing resin in a cavity of the mold is too high, there may be a gap between the upper mold body 24 and the surface of the heat spreader. This can allow the sealing resin to bleed into the gap, thereby causing the resin-bleeding defect.
FIGS. 3 and 4 illustrate a typical method of molding a semiconductor package.
Referring to FIGS. 3 and 4, a technology of forming a dam 28 on a heater spreader 18 of a semiconductor package 20′ to prevent the resin bleeding defect is discussed in U.S. Pat. Publication No. 2002/0076856 to Richard W. Wensel, Boise entitled “METHOD AND APPARATUS FOR TRANSFER MOLDING ENCAPSULATION OF A SEMICONDUCTOR DIE WITH ATTACHED HEAT SINK” published on Jun. 20, 2002.
FIG. 4 shows an enlarged view of a portion B of FIG. 4.
As shown in FIG. 4, the dam 28 formed on a surface of the heat spreader 18 is designed to block the undesirable bleeding of the sealing resin 20. When transfer pressure applied by a ram to transfer the sealing resin to a cavity of the mold is excessively high, however, the dam 24 cannot perfectly contact an upper mold body 24 (FIG. 4). Thus, the dam 28 cannot always effectively block the bleeding of the sealing resin that causes the resin bleed defect.